Constant frequency escapement mechanism



Nov. 15, 1966 G. s. WESTERMAN 3,285,173

CONSTANT FREQUENCY ESCAPEMENT MECHANISM Filed Sept. 29, 1964 2 Sheets-Sheet 1 INVENTOR. v GEORGE S. WESTERMAN I ,M W

ATTORNEYS Nov. 15, 1966 G. s. WESTERMAN 3,285,173

CONSTANT FREQUENCY ESCAPEMENT MECHANISM Filed Sept. 2.9, 1964 2 Sheets-Sheet ,2

L 7 INVENTOR.

60 3a 74 GEORGE SWESTERMN 5 28 7M" ATTORNEYS United States Patent 3,285,178 CONSTANT FREQUENCY ESCAPEMENT MECHANISM George S. Westerman, Cinnaminson, N.J., assignor to the United States of America as represented by the Secretary of the Army Filed Sept. 29, 1964, Ser. No. 400,281 1 Claim. (Cl. 102-84) The invention described herein may be manufactured and used by or for the Government for governmental purposes without the payment to me of any royalty thereon.

This invention relates to timing mechanisms and, more particularly, to timing mechanisms associated with projectile fuzes.

In time movements of mechanical time fuzes, the escapement area that meters out time is a most critical one. Normally, a block, which is adjustable to a predetermined set position, supports the free ends of -a hairspring that controls the beat frequency or oscillation of the escapement lever in the timer. However, when subjected to high speed rotational environment, the hairspring has a tendency to stiffen from the effects of centrifugal force resulting in a decrease in its deflection, which in turn increases the beat frequency. The increase in beat frequency normally makes the timing movement run faster than that for which it had been adjusted. Thus, when precision timing is required particularly in a projectile fuze environment, a deviated setting of the timer from its regulated adjustment is necessary in the field. In copending application, Serial Number 394,367, filed September 3, 1964, a mechanism is provided which eliminates the need for such deviated settings previously required in the field for use in a high spin environment. In that mechanism, the support structure for the hairspring ends are movable in a high speed rotational environment by centrifugal force against a respective biasing spring which is seated at the outer end of the corresponding housing passageway. While this arrangement does produce a more constant hairspring beat frequency operation, it does have certain aspects or conditions susceptible to improve ment with which the present invention is concerned. It has been found that springs apparently similar to each other in most other respects often have a variance in spring rates, such that when employed in the desired operative environment varying beat frequencies would result.

It is a primary object of the invention to provide a timing mechanism adapted to operate with the maximum degree of accuracy at a constant predetermined beat frequency when subjected to variable speed effects of rotation greater than that for which it was basically regulated. A further object of the invention is to provide such an accurate timing mechanism having means including a biasing spring capable of compensating for tendencies of its hairspring frequency to deviate when placed in a dynamic environment and means for minutely adjusting the spring bias to compensate for variations in spring rates.

These and other objects and advantages of the invention will become apparent from the fol-lowing description and accompanying drawings in which:

FIG. 1 is an elevational view partly broken away in section to show the timing mechanism of a projectile fuze;

FIG. 2 is a sectional view taken along line 2-2 of FIG. 1;

FIG. 3 is a sectional elevation view of a preferred support arrangement for an end of the hairspring shown in FIG. 2;

3,285,178 Patented Nov. 15, 1966 FIG. 6 is a view similar to FIG. 2 with certain parts I removed or in section and others enlarged showing the escapement area of the mechanism.

The projectile fuze, generally shown at 10 (FIG. 1), is provided with rearwardly located attaching or threaded means 11 for connection to a forward portion of projectile body 12 as the forward nose portion thereof. The timer mechanism or movement assembly shown generally at 13 is mounted within the fuze for rotation therewith as the projectile spins during its flight. The mechanism 13 includes a spirally wound spring 14 having its outer end attached or secured to a fixed internal member 16 and its inner end connected to central shaft 18 rotatably positioned about a longtudinal axis of the fuze. Gear 20 carried by shaft 18 is interconnected by gear train elements 21, 22, 23, 24, 25, 26 to escapement gear 27 which is driven by gear 26 carried by common shaft 28. Escapement gear 27 (FIGS. 2, 6) is thus biased by the stored energy in spirally wound spring 14 for rotation as controlled by the pallets 30, 31 of an oscillating escapement lever 32'. The radially central portion 35 of shaft 33 carrying escapement lever 32 is rigidly connected to hairspring 34 sub stantially at the mid-point thereof through which passes the spin axis of the entire projectile. Each of the hairspring free ends 36, 37 is positioned in appropriate slots or grooves 38 (FIGS. 5, 6) of an upstanding leg member 39 of an adjustable and self-compensating support arrangement generally shown at 40 (FIGS. 3, 6) and to be more fully described hereinafter.

Referring again to FIG. 1, firing pin 41 is cocked with its shaft 42 spring loaded and which when released will ignite detonator 43. Compression spring 44 on shaft 42 is compressed between shaft collar 45 and a suitably recessed shoulder 46 on a stationary member of the movement assembly 13. A locking cam 47 (FIGS. 1, 4), for normally retaining collar 45 in a retracted position, is pivotally carried by post 48 suitably journalled in fixed or stationary members or plates 49 of the movement assembly. A torsion spring loaded shaft 50 (FIG. 4), appropriately in stationary movement assembly members, normally engages cam 47 in the cocked position of firing pin collar 45 until the timing mechanism has run its predetermined time when a circumferential opening 52 in timing disk 53 rotated by shaft 18 is aligned with and receives an offset projection 54 of the thusly rotated shaft 50. Minute predetermined rotation of shaft 50 and recess 55 therein will immediately free cam 47 to be withdrawn from locking the firing pin collar 45, enabling the spring biased firing pin 41 to stab or ignite the detonator.

Preferably, each hairspring end 36, 37 is provided with a support arrange-ment 40 having an upstanding slotted leg 39 that is confined to movement along a predetermined straight line extending through the hairspring and escapement lever central connection 35, and which slidin-gly supports its respective hairspring end at respective positions such that the central connection 35 is at all times equidistant therefrom. Each of the support arrangements 40, symmetrically positioned about the hairspring and lever connection 35, includes a block body 60 (FIGS. 3, 5, 6) which preferably has cut-away portions formed in the lower part of its side walls 61, 62 to define a centrally located, longitudinally extending depending portion 63 that is positioned in radially extending groove means 64 provided in support plate 65. Each block 60 is provided with a lengthwise, central cylindrical bore or passageway 66 and an aligned counterbore 67 that respectively receive the innermost 68 and intermediate 69 portions of adjusting screw 70, the threaded head of which has a slot 71 for facilitating translation in tapped opening 72 of plate 65 lengthwise of hairspring, 34 and relative to central connection 35. The intermediate portion 69 of adjusting screw 70 is of larger diameter than innermost portion 68 to define shoulder 73 and has an outer threaded portion 69 adjacent the relatively enlarged and coarser threaded screw head. =Minutely adjustable star nut 74 positioned upon relatively fine threads 69 has an inwardly directed hub or sleeve 75 for facilitating seating one end of a compression spring 76. The spring 76, while of predetermined design, does have a spring rate or spring constant which often varies for a given design due to slight characteristic deviations trom spring to spring, resulting in a precisely indeterminable effective inward force by the other end of spring 76 upon the adjacent outer surface of corresponding block 60. The innermost portion 68 of the screw 70 is appropriately grooved at 78 (FIG. 5) to receive a suitable keeper arrangement 77 for retaining block 60 upon screw 70. The proportional dimensions of adjusting screw '70 and its receiving block passageway 66, 67 are such that a basic regulation adjustment of screw 70 within plate 65 will position the associated parts at predetermined positions with shoulder 73 adapted to serve as -a maximum stop for outward movement of block 60 in the absence of star nut 74 and associated spring 76 being in a properly adjusted position to provide the stop or abutment function. Even though the support arrangements 40, 40 are substantially identical and symmetrically arranged on opposite sides of radially central portion 35, the spring rates of individual springs 76, 76 may not be sufficiently equivalent to produce equal and opposite inward forces upon respective blocks 60 as required in the precision mechanism. However, slight or minute adjustment of one or both star nuts 74 may be made to adjust the corresponding spring constant or bias of spring(s) 76 so that the inward forces upon each block are equated for a given high speed rotational environment. This will assure symmetrical block and leg 39, 39 movement under the operational influence of centrifugal force.

At high speed operating conditions, the resulting balanced or symmetrical outward movement of legs 39 and their supporting grooves 38 will increase the effective length of the hairspring to compensate for any tendency that centrifugal force effects would have upon the beat frequency of the timer. Should the hairspring beat frequency be too high, the star nuts are translated radially outward by counter-clockwise rotation, permitting corresponding leg 39 to move further outward and reduce the frequency. Conversely, if running too low, inward trans lationa-l adjustment is made. Thus, the hairspring can maintain its normal reciprocato-ry movements between defiected S positions, one of which is shown in dotted lines illustrating the hairspring ends 36 37 (FIG. 6), in assisting the escapement lever to accurately control the metering of timer power output.

Various modifications or changes may be resorted to without departing from the scope of the invention as define-d in the appended claim.

I claim:

In a high speed rotatable projectile fuse timing mechanism having an oscillatory escapement lever for metering timer power output, a hairspring having a central portion connected to a central portion of said lever and controlling the oscillation of said lever, and means supporting end portions of said hairspring, said support means including a pair of blocks each slidab-ly mounted in a passageway substantially symmetrically positioned about a common center line passing through said lever and hairspring connection, means for biasing one end of each block towards said connection, and means connected to each block and slidingly receiving a respective hairspring end portion, so arranged that each block may be moved against its biasing means for adjusting the effective lengths of said hairspring to maintain a substantially constant predetermined beat frequency in the timing mechanism when the latter is subjected to high speed rotation, the improvement comprising separate means slida-bly receiving a respective one of said blocks and carrying a respective one of said biasing means, each of said biasing means including a compression spring and means adjust-able along the corresponding carrying means for varying the respective spring rate, and said separate means including independently basic adjusting means along said common center line, by virtue of which precise compensating adjustments may :be available to overcome even the slightest deviations in the spring characteristics.

References Cited by the Examiner UNITED STATES PATENTS 1,577,391 3/ 1926 V-araud 102--84 2,406,730 8/1946 Whitehead 581 17 3,168,833 2/1965 Popovitch 10284 X BENJAMIN A. B-ORCHELT, Primary Examiner.

G. H. GLANZMAN, Assistant Examiner. 

